Referring to FIG. 1, a printhead assembly 230 for a high-speed or high throughput, multicolor image producing or printing machine is shown. The assembly 230 is coupled to a controller 200 configured to control the operation of the printhead assembly and more particularly to direct the printheads of the assembly to produce an image from captured image data. For certain machines, the controller 200 may also control at least one actuator 220 that is operable to move the printhead relative to the substrate receiving the image. The assembly 230 shown in FIG. 1 includes two printheads 232 and 236, each having a corresponding front face 233, 237 and nozzle array 243, 245 for ejecting ink onto the substrate to form an image. It can be appreciated that an imaging or printing machine may include more than one printhead assembly 230 and more than the two printheads shown in FIG. 1. Although a solid-ink printhead is depicted in the drawings, other printheads and printing or imaging machines are contemplated. In addition, a partial width printhead is shown, but other printheads, including full-width and reciprocating array printheads are contemplated.
Each printhead 232, 236 is rigidly mounted to a carrier plate or ball plate assembly that may itself be rigidly mounted to a translation carriage controlled by the actuator 220. Thus, in a typical installation, the printheads are mounted to the carrier plate assembly by a plurality of fasteners 250. One such arrangement is shown in FIGS. 2-3. The printhead 232 is shown mounted to a carrier plate assembly 260 in FIG. 2 by a screw-type fastener 250. As shown in more detail in FIG. 3, the fastener 250 includes a shank 252 terminating in a threaded tip 254 configured to thread into an internally threaded boss 262. The head 256 of the fastener may incorporate a hex-feature for engagement with a driving tool to rotate the fastener/screw 250. A spring 258 is mounted between an enlarged portion 257 of the head 256 and a mounting flange 239 of the printhead. A snap-ring 259 may be used to capture the fastener on the mounting flange 239. As the fastener is tightened into the threaded boss 262 of the carrier plate assembly 260 the spring bears against the mounting flange 239 to press the printhead 232 against a surface 264 (FIG. 4) of the carrier plate assembly to form a fluid-tight seal.
It is important that the printhead be properly engaged with the carrier plate assembly or ball plate to provide a fluid-tight engagement and to ensure that the printhead is correctly registered with the image-receiving substrate. When the printheads are replaced, care must be taken that the fasteners 250 are adequately and properly tightened to produce this proper engagement. Thus, in one procedure, each printhead 232, 236 is mounted using two fasteners 250, as shown in FIG. 1. To ensure proper seating of the printhead, the fasteners or screws 250 are tightened in alternating fashion until each screw is seated. The mating threads 254 typically have a fine pitch so multiple rotations of each fastener 250 is required to fully tighten each screw and seat the printhead. In order to ensure proper seating, the installation procedure typically requires making two full turns on one fastener, two full turns of the other fastener, and then repeating this sequence a second time to seat the printhead.
It can be appreciated that engaging the head 256 of each fastener in alternating fashion with a driving tool can be cumbersome and time consuming. Since the typical procedure requires a precise number of screw rotations for each step, it is not well-suited for use of a power driving tool. Thus, the driving tool must be a manual tool, such as a hex wrench, which can lead to user fatigue when replacing several printheads at one time, as frequently occurs. Moreover, unless a torque wrench is used there is always the risk that a customer will over-tighten a fastener which can lead to stripping of the threads or even fracture of the boss 262. It is desirable to provide a mechanism for mounting printheads to carrier plate or ball plate assemblies that is easier and more convenient to operate.